Electrode material

Abstract

An electrode material is provided for electrochemical sensors, particularly for sensors detecting combustible gases. For these types of applications, perovskite electrode materials are known which, however, by modification of their oxygen stoichiometry, have a considerable charge carrier mobility. These defects are the causes for an additional, catalytic activity with oxidation processes at electrodes. The measurement of hydrocarbons from combustible gases is thus distorted with electrode materials of this type. These disadvantages are overcome by making such electrode materials from mixed oxides with non-perovskite crystalline structures, which have chemical compositions of one or more of the following general formulas: (A/D) 3-y B x C 5-x O 12 ±δ, D 1-y B 1-x C x O 4 ±δ, D 2-y B 8-x C x O 16 ±δ, D 2-y B 1+x C 1-x O 5 ±δ, or D 2-y B x C 2-x O 7 ±δ, wherein A and D are respectively sub-stoichiometrically used cations of the lanthanide series and the alkaline earth metal group, A/D means a cation selected from A, D and mixture thereof, B is a multivalent ion, and C is a redox-stable ion.

We claim: 
     
       1. An electrode material for electrochemical sensors, comprising a mixed oxide having a non-perovskite crystalline structure and having a chemical composition of a general formula selected from the group consisting of: (A/D) 3-y  B x  C 5-x  O 12 ±δ,   D 1-y  B 1-y  C x  O 4 ±δ,   D 2-y  B 8-x  C x  O 16 ±δ,   D 2-y  B 8+x  C 1-x  O 5 ±δ, and   D 2-y  B x  C 2-x  O 7 ±δ wherein A and D are respectively sub-stoichiometrically used cations of the lanthanide series and the alkaline earth metal group, and A/D means a cation selected from A, D and mixtures thereof, B is a multivalent ion, and C is a redox-stable ion, x and y are selected such that A and/or D and at least one of B and C is present in the mixed oxide, and δ represents a possible charge compensation for minor imperfections in oxygen partial lattice of the crystalline structure.     
     
     
       2. The electrode material according to claim 1, wherein the multivalent ion B is a transition metal. 
     
     
       3. The electrode material according to claim 2, wherein the transition metal is selected from the group consisting of Cr, Mn, Co, Fe and Ni. 
     
     
       4. The electrode material according to claim 1, wherein the redox-stable ion C is selected from the group consisting of Al, Ga, Nb, and Ta. 
     
     
       5. The electrode material according to claim 1, comprising compounds of the general formula (A/D) 3-y  B x  C 5-x  O 12 ±δ, wherein x ranges from 0.005 to 2.995. 
     
     
       6. The electrode material according to claim 1, comprising compounds of the general formula D 1-y  B 1-x  C x  O 4 ±δ, wherein x ranges from 0.005 to 0.995. 
     
     
       7. The electrode material according to claim 1, comprising compounds of the general formula D 2-y  B 8-x  C x  O 16 ±δ, wherein x ranges from 0.005 to 7.995. 
     
     
       8. The electrode material according to claim 1, comprising compounds of the general formula D 2-y  B 1+x  C 1-x  O 5 ±δ, wherein x ranges from 0.005 to 0.995. 
     
     
       9. The electrode material according to claim 1, comprising compounds of the general formula D 2-y  B x  C 2-x  O 7 ±δ, wherein x ranges from 0.005 to 1.995. 
     
     
       10. The electrode material according to claim 1, wherein y ranges from 0.005 to 0.4.